1,720,983 research outputs found
Visible photonic bandgap engineering in silicon nitride waveguides
Full text linkWe demonstrate experimentally the tuning of complete photonic band gaps in patterned silicon nitride waveguides. Transmission measurements were performed using an ultrabroadband high-brightness white light laser continuum, extracting extinction ratios as low as 10–4 in the gap regions. Angle-resolved measurements show the perfect alignment of the gap around the Γ-J direction
Self-phase modulation induced spectral broadening of ultrashort laser pulses in tantalum pentoxide (Ta<sub>2</sub>O<sub>5</sub>) rib waveguide
No full textSelf-phase modulation induced spectral broadening has been observed for ultrashort pulses propagating through Ta2O5 rib waveguide. The associated nonlinear refractive index was estimated to be 7.23 x10-19 m2/W, which is higher by one order of magnitude than silica glass
Complete and absolute photonic bandgaps in highly symmetric photonic quasicrystals embedded in low refractive index materials
No full textIt is firmly established that periodic lattice structures can support photonic bandgaps (PBG). However, complete and absolute photonic bandgaps (CAPBG) have only been achieved in high dielectric constant mediums such as GaAs (ε=13.6). An artificial quasiperiodic photonic crystal based on the random square-triangle tiling system was designed and fabricated. The photonic quasicrystal possesses 12-fold symmetry and was analysed using a finite difference time domain (FDTD) approach. High orders of symmetry in photonic quasicrystals have been shown to provide isotropic bandgaps across all the directions of propagation of light. As an outcome of these properties, this new class of photonic quasicrystal has been shown, for the first time, to possess a secondary non-directional CAPBG for a relatively low index material, silicon nitride (ε=4.08). These materials are compatible with integrated optical technologies. This allows the fabrication of efficient integrated optical PBG devices such as WDM filters and multiplexers to become a real possibility
Self refractive non-linearities in chalcogenide based glasses
No full textWe report third order non-linear absorption and refraction measurements at 1.20µm and 1.52µm on selected gallium–Lanthanum sulfide-based glasses (Ga:La:S) showing negligible non-linear absorption and a refractive non-linearity close to one hundred times that of SiO2. Their potential use in telecommunication as base materials for all-optical switching practical devices is evaluated resulting in large figures of merit. The addition of a glass modifier to the Ga:La:S matrix has improved thermal and optical properties, resulting in ease of fibre drawing. The non-linear optical response of this new variant of the Ga:La:S family is studied
Separation of photonic crystal modes using femtosecond time-of-flight measurements in a waveguide
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Highly engineered mesoporous structures for optical processing
No full textArranging periodic, or quasi-periodic, regions of differing refractive index in one, two, or three dimensions can form a unique class of mesoporous structures. These structures are generally known as photonic crystals, or photonic quasicrystals, and they are the optical analogue of semiconducting materials. Whereas a semiconductor's band structure arises from the interaction of electron or hole waves with an arrangement of ion cores, the photonic crystal band structure results from the interaction of light waves with an arrangement of regions of differing refractive index.What makes photonic crystals highly attractive to the optical engineer is that we can actually place the regions of differing refractive index in a pattern specifically tailored to produce a given optical function, such as an extremely high dispersion, for example. That is, we can define the geometrical arrangement of the dielectric foam to provide us with the form of band structure we require for our optical functionality.In this paper, the optical properties and applications of these highly engineered mesoporous dielectrics will be discussed
Optical spectroscopy of neodymium-doped tantalum pentoxide slab waveguides
No full textNeodymium doped tantalum pentoxide (Nd:Ta2O5) waveguides were fabricated by RF sputtering from a Nd doped Ta2O5 target. Waveguide losses, absorption spectra, fluorescence spectra and excited-state lifetime were measured, and show promise for realisation of waveguide lasers
Silicon-based photonic crystal structures
No full textIt is likely that the commercialisation of Photonic Crystal (PC) technology will require the high-volume capabilities provided by semiconductor nanofabrication processes. To this end, a Silicon-compatible PC waveguide could form the basic building block of an all-optical circuit. This presentation will discuss the development of PC research at Southampton University (UK) which began with deep photoelectrochemically etched holes in single-crystal Silicon. This initial work progressed to an all dielectric waveguide structure on a Silicon substrate, with the materials utilised being compatible with a CMOS process. PC nanofabrication and optical characterisation using these waveguiding structures will be described in detail
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